Summary of Work: The Statistical Consulting Service was formally established in 1997 to provide a variety of experimental design and data analysis support to NIEHS research efforts. These activities range from routine data analysis to more comprehensive collaborations that result in co-authorship of papers in the subject matter literature. More than 50 NIEHS scientists, representing a number of different areas of environmental health research, made use of the Statistical Consulting Service this year. The list of publications that accompanies this Project Report provides more information as to the nature of these research collaborations. Specific examples of collaborative research activities involving the Statistical Consulting Service include an investigation of the biological significance of decreased tumor incidences, a study of the effects of Helicobacter hepaticus on tumor incidence, an investigation of the relationships among reproductive endpoints in Swiss mice, and an evaluation of chemically-induced skin tumors in TG.AC mice. The Statistical Consulting Service offered a Statistics Mini-course in April 1997 that was attended by approximately 40 Institute scientists.